Tube forming device



F. v. COLLINS -TUBE FORMING DEVICE Feb. 8; 1949. y

Filed Deo. 51, 1947 y www j Jn/W25@ fw/2m@ //AM7//// A Patented Fel.l 1949 4TUBE FORMING DEVICE Fred V. Collins, Des Plaines, Ill., assignor to vWilliam F. Stahl, Kenilworth, Ill.

Application December 31, 1947, Serial No. 794,849 4 claims.. (ci. 154-42) This invention is directed to an apparatus for forming tubes from fusible flat web material and is an improvement over the apparatus disclosed in my co-pending application Ser. No. 751,693 flied June 2, 1947. y

The tube forming apparatus of said co-pending application includes a mandrel., means `for advancing the web of fusible material forwardly of the mandrel and into tubular form thereabout and means including a wave guide for directing high frequency radio waves toward the edge portions of the tube to fuse or seal the edge portions to form completely the tube. Such apparatus has worked quite well and satisfactory results have been obtainedthereby. However, no pressure was applied to the seal during the sealing operation and the high frequency radio waves were not highly concentrated at the seal. As a result, considerable high frequency energy was required to fuse or seal successfully the edge portions of the tube.

The principal object of this invention is to provide an improved tube forming apparatus having a wave guide for the high frequency radio waves wherein pressure is applied to the seal during the fusing or sealing operation, wherein the high frequency radio waves are highly concentrated on the edge portions of the tube for fusing purposes and whereby an improved seal is obtained with a lesser amount of high frequency energy.

In carrying out this object of the invention the wave guide is constructed to direct the high frequency radio waves toward the edge portions of the tube, and a substantially hollow roller receives the and of the wave guide. The roller is provided with a rim of material having a relatively high dielectric constant and low power factor which engages the edge portions of the tube to apply pressure thereto during the fusing or sealing operation. vPreferably the rim of the roller has a narrow tread surface for concentrating the high frequency radio waves at the fusion point.

Further objects of this invention reside in the details of construction of the tube forming apparatus and the cooperative relationship between the component parts thereof,

Other objects and advantages will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawing in which:

Fig. 1 is a sectional view through a portion of the tube forming apparatus and Fig. 2 is a sectional view taken substantially along the line -2-2 of Fig. 1.

In the specific illustration given in Fig. 1 the tube forming apparatus includes a mandrel I preferably made of metal and having a longitudinal bore I3 therein. The mandrel I0 is secured to a suitable supporting frame Ii by screws I2. The mandrel is provided with an extension I4 electrically insulated therefrom by a spacer I5 made of insulating material. The extension Il and spacer I5 are also provided with a longitudinal bore in alignment with the longitudinal bore in the mandrel III.

A pair of tubular guide members I'I having substantially conical entrances I8 surround the mandrel Iii in spaced relation thereto. The tubu lar guide members lI are connected together by a strap I9 and one of the tubular guide members is provided with an extension for the purpose of securing both guide members to the mandrel. The securing means includes a spacer 2| and a screw or pin 22. A folder 23 is also secured to the mandrel I0 adjacent the spacer 2| and the folder 23 is preferably provided with slots for receiving the edge portion of the fusible web as it is advanced along the mandrel.

The web of fusible material is designated at 25 and it may be a thermo-plastic material having a relatively high power factor such as cellulose-acetate, vinyl acetate, vinyl chloride (copolymer) or any other suitable fusible material. The web 25 is advanced along the mandrel I0, enters the slots in the folder 23 and then enters the tubular guide members I'I, whereby the edge portions of the fusible web are brought together or overlapped as indicated at 26. A pair of rollers 21 having resilient tires 28 are rotated for the purpose of advancing the tube along the mandrel.

After the edge portions of the web of fusible material are brought together as at 26 they are fused to form a seam therebetween by means of high frequency radio waves which are produced by a suitable high frequency energy generator 30. The output of the high frequency generator 30 may be coupled in any suitable manner as by a hair pin type loop 3i with a wave guide 32. The wave guide 32 may be of any accepted form and may be rigid or flexible and formed of any suitable material. The wave guide 32 is preferably provided with an elbow 34 terminating in a downwardly turned nozzle 35 for directing the high frequency radio waves toward the edge portions of the tube to be fused. The length of the wave guide 32 is preferably such that the nozzle 35 thereof is located at a desirable point based on ss,

the mode of oscillation such as TE, TEo-i, TM,

Menara etc. and on the reflecting characteristics of the web material and mandrel for obtaining maximum power and concentration of the high frequency radio waves guided thereby at the overlapped edge portions of the fusible material.

The elbow Il and nozzle 3l of the wave -guide are included in`a substantially hollow roller having sides and 31 provided with hubs 38 and 38 respectively. The hub 3B is Journaled by a bearing 4o in a bracket u and the hub as is Journaled by a bearing 4'2 in a bracket 43 which in turn is secured tothe bracket 4i by screws 44. The wave guide extends through the hub 38 of. the roller. Thus. the wave guide I2 'and its nozzle 3B remain substantially stationary Awhile at the same time the substantially hollow roller containing the nozzle is permitted to rotate.

The bracket 4I is vertically. slidably connected by a tongue and groove connection 4B to a stationary bracket Ily whereby the bracket 4i and the substantially hollow roller carried thereby are permitted to move upwardly or downwardly.

The roller is provided with e. rim 49 of material having a high dielectric constant and also preferably of relatively low power factor, for example, the rim may be made from ceramic such as porcelain or steatite or titanium oxide materials or thermo-plastics such as polystyrene,

polyethylene and polytetrailuoroethylene. These materials are characterized by having high dielectric constant and low power factor characteristics whereby they pass the high frequency radio waves with little loss in energy and with very little heating therein. The rim te is suitably secured to the sides 36 and tl of the roller and is preferably substantially triangular in cross-'section to present a narrow tread surface 50. The tread surface engages the edge portions 26 of the tube being formed and the roller by means of its own weight or by a spring (not shown) applies a pressure to the edge portions as they are being fused by the high frequency radio waves passing therethrough. The roller in addition to providing pressure at the fusing point also operates effectively to. concentrate more highly the high frequency energy at the fusing point. The cross-sectional shape of the rim i! operates in a "quasi-optical manner to accomplish this function.

By reason of the higher concentration of high frequency energy and the application of pressure on the edge portions of the tube during the fusing thereof a greatly improved seam therebettween is provided with less expenditure of high frequency energy.

1. Apparatus for formingitubes from fusiblev flat web material. comprising a mandrel, means for advancing'said web forwardly of said mandrel and into tubular form. and means for subjecting the edge portions of said tube to high frequency radio waves to fuse said portions includinga wave guide for directing high frequency radio waves toward the edge portions of said tube, a substantially hollow roller receiving the end of the wave guide and a rim of high dielectric-constant material on the roller for engaging the edge portions of the tube.

2. Apparatus for. forming tubes from fusible flat web material, comprising a mandrel, means for advancing said web forwardly of said mandrel and into tubular-form, and means for subjecting the edge portions of said tube to high frequency radio -waves to fuse said portions including a substantially hollow roller having a rim of high dielectric-constant material engaging the edge portions of said tube and a wave guide entering the hub of the roller and having an elbow disposed within the roller for directing the high frequency radio waves through the rim toward the edge portions of the tube.

3. Apparatus for forming tubes from fusible flat web material. comprising a mandrel, means for advancing said web forwardly of said mandrel and into tubular form, and means for subjecting the edge portions of said tube to high frequency radio waves to fuse said portions including a wave guide for directing high frequency radio waves toward the edge portions of said tube, a substantially hollow roller receiving the end of the wave guide and a rim of high dielectric-constant material on the roller and having a narrow tread surface for engaging the edge portions of the tube and concentrating the high frequency radio waves thereon.

Apparatus for forming tubes from fusible fiat web material, comprising a mandrel, means for advancing said web forwardly of said mandrel and into tubular form. and means for subjecting the edge portions of said tube to high frequency radio waves to fuse said portions including a substantially hollow roller having a rim of high dielectric-constant material provided with a narrow tread surface for engaging the edge portions of said tube and a wave guide entering the hub of the roller and having an elbow disposed within the roller for directing the high frequency radio waves through the rim toward the edge portions of the tube, said rim concentrating the high frequency radio waves thereon.

FRED V. COLLINS.

REFERENCES CKTED The following references are of record in the OTHER REFERENCES lvigcrowaves, Product Engineering, Jan. 1947, p. 1 

